i#2522 strcasestr prototype error: Remove const from result type

[xdje42]

The definition of strcasestr is

char *strcasestr(const char *text, const char *pattern);

but drmemory uses

const char *strcasestr(const char *text, const char *pattern);

This causes build errors when both /usr/include/string.h and common/utils.h are included in linux. The definition for strcasestr for C has always not had the const in the result type (going back to its original addition to glibc in 1997). Thus we're pretty safe in not breaking anything on *nix. The other main use case of drmemory's strcasestr is on Windows, which does not have strcasestr.

Tested:
$ cmake && make
Also, there are failures in the clang and x86 workflows, but comparing the logs before/after
shows all failures pre-exist this patch, no new failures.

Here is the complete audit, all failures are pre-existing.

Recorded (errantly) as i#1938 failures:

• wrap_operators: "internal crash" (Received SIGSEGV)
  • filed as CRASH: SIGSEGV in wrap_operators test in ci-clang workflow #2535
• wrap_cs2bug: CHECK_TRUNCATE_TYPE_sbyte(new_offs) (All wrap_ 32-bit tests hit DR assert core\ir\x86\encode.c:2722 CHECK_TRUNCATE_TYPE_sbyte(new_offs) on GA CI #2342)
• pcache-use: "Usage error: meta-instr faulted? must set translation field and handle fault!" (ASSERT pcache-use "meta-instr faulted?" #2202)
• app_suite: vsyscall incorrect assumption (ASSERT "vsyscall incorrect assumption" on AMD 32-bit #2491)
• app_suite.pattern: assert failure: save->ignore_next_delete == 0 (premature deletion)
  • filed as i#2537
• fuzz_threads: vsyscall incorrect assumption (ASSERT "vsyscall incorrect assumption" on AMD 32-bit #2491)

Note: The above are marked as expected failures but runsuite_wrapper.pl hardwires the addition of "i#1938" to test output. #2534

Not currently recorded as expected failures (all #2491 - vsyscall incorrect assumption):

• selfmod
• syscalls_unix
• clone
• pthread_test
• realloc

Fixes #2522

[derekbruening]

@xdje42 external users seem to be hitting this issue, would be good to get this merged: https://groups.google.com/g/dynamorio-users/c/WeQqxjwuPDI